Such illumination systems are known per se. They are used, inter alia, as luminaire for general lighting purposes, for example, for office lighting, for shop lighting or, for example, for in-home general lighting purposes.
The luminescent material generally absorbs part of the light emitted by a light source of the color-tunable illumination system and converts the absorbed light into light of a different color. The luminescent material is often arranged at a distance from the light source. This configuration is also referred to as a remote phosphor configuration. A benefit when using the remote phosphor configuration is that the conversion efficiency and the life-time of the luminescent material are improved and that the range of luminescent materials to choose from is improved.
Such a color-tunable illumination system is known from U.S. Pat. No. 6,357,889 in which a color tunable light source includes multiple light emitting components, such as light emitting diodes (also indicated as LEDs) or laser diodes (also indicated as LDs), with different emission wavelengths, and multiple phosphors with different excitation and emission wavelengths. The emission wavelengths of the different light emitting components are chosen to match the excitation wavelengths of the different phosphors. The light emitting components are powered by an electrical circuit which allows separate control of the optical power output of the different wavelength LEDs and/or LDs. The light from the light emitting components is arranged to impinge on the combination of phosphors such that the phosphors are excited and emit light at their characteristic wavelengths. By separately adjusting the power to each LED and/or LD, the amount of light emitted by each phosphor, and hence, through color mixing, the color of the light emitted is varied.
A disadvantage of the known color-tunable illumination system is that the known illumination system is relatively expensive.